A spokesman for Biffa said: "There are a number of phases of works that are planned over the following few weeks and the works include installation of 100 gas extraction wells, temporary lining of waste flanks, replacement of chamber well heads and a full review of our management plans.

"Works have been in progress all week and will continue until all actions agreed with the EA have been completed. We expect a gradual improvement in the situation as works progress.

"Biffa apologies for the inconvenience it has caused the local community and we are working hard on improving the situation."

An Environment Agency spokesman said on Thursday (January 30) that the increase in complaints, which stood at 75 on January 23, had mainly come in the previous 24 hours.

"It will take a further 10 days before these wells are completed and working," the spokesman said.

"We are monitoring the action plan and odour complaints including site/area inspections. The situation should improve over the next 10 days as more wells come online and gas is captured.

"There will be a full site review in early February to see whether further actions are needed."

If the action plan is not met, the agency could use enforcement powers which include a variation of permit conditions, a fine or suspension or revocation of environmental permits and licences.

A statement from the Green Party borough councillor for Redhill East, Bryn Truscott, said: "Smells do occur from the site year round, but the stink has been extraordinary recently, with reports from Earlswood and Reigate and even from people on passing trains.

"Biffa is installing more gas infrastructure and if this does solve the problem, we should start to smell the benefits in about a week."

The Environment Agency is still encouraging people to call its incident hotline on 0800 80 70 60 with complaints.